Snap action diaphragm type liquid pump



Jan. 17, 1961 E. M. BROHL 2,968,254

SNAP ACTION DIAPHRAGM TYPE LIQUID PUMP Filed April 15, 1957 Z H H I" I I I 444 f/ 3 I I l if INVENTOR. az/Xfizai! SNAP ACTION DIAPHRAGM TYPE LIQUID PUMP Earl M. Brohl, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 15, 1957, Ser. No. 652,997

3 Claims. (Cl. 103-150) This invention relates to liquid pumps and more particularly to liquid pumps of the diaphragm type such as employed in automotive engine fuel systems.

As heretofore conventionally practiced, the pressure of liquid in the pumping chamber of a diaphragm pump, when plotted against time, crudely attempts to follow a sine wave development because of the reciprocation of the diaphragm. This reciprocation is due to the action of a rocker arm during each suction stroke and the stored energy of a compressed pump spring during each pumping stroke. Various methods and structures have been utilized to increase the capacity of such pumps and it has been recognized that if the time interval for admitting liquid to the pumping chamber were increased in each operative cycle, the capacity of the pump also would be increased. Referring to this observation another way; if the attempted sine wave pressure development were changed to approach to some extent what may be termed a square wave pressure operation, it would appear that the inlet time and, hence, the capacity of the pump would be increased.

To these ends, an object of the present invention is to provide an improved liquid pump of the diaphragm type which is capable of a large capacity discharge.

A feature of the invention is a snap action toggle mechanism connecting a liquid pump diaphragm with a power actuated element such as a rocker arm.

This and other important features of the invention will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawings:

Fig. 1 is a sectional view through a fuel pump of the diaphragm type in which the present invention is embodied taken on line 1-1 of Fig. 2; and

Fig. 2 is a sectional view taken along the line 2-2 in Fig. 1. I

The drawings show a pump housing generally indicated at which comprises a pump portion 12 and a support portion 14. The pump portion 12 is provided with a cap 16 attached thereto by means of peripheral screws 18 and a central screw 19. The portion 12 is also provided with an inlet passage 20 as well as an oppositely disposed outlet passage 22 and is divided by a partition 24 to form an inlet chamber 26 and an outlet chamber 28.

The bottom wall of the pump portion 12 is recessed to form a pumping chamber 30 and this chamber is defined by a flexible diaphragm 32 interposed between the portions 12 and 14 and clamped in position as is conventional in such structures. Screws 18 are of sufiicient length to aid in the clamping function. The upper wall defining the pumping chamber 30 comprises a horizontal partition 34 which is integral with the partition 24 and which supports a pressure actuated inlet valve 36 as well as a similarly constructed valve 38 serving as an outlet valve. Further details regarding the pump portion 12 and the elements therein are not set forth herein as they are fully disclosed in the United States Patent No. 2,713,-

United States Patent O 830 granted July 26, 1955, in the names of G. W. Harry and W. E. Barnes.

The support portion 14, as viewed in Fig. 1, has a generally L-shaped chamber 40 an open end of which passes through a flange portion 42 which is adapted to be attached to the wall of a crankcase by means not shown. The other end of the chamber 40 is cylindrical 'as at 41 to permit oscillation of the diaphragm 32. An intermediate portion of the chamber 40 is provided with opposed fiat walls 43 and 44 as seen in Fig. 2. A rocker arm 45 is pivotally arranged within the support portion 14 and is adapted to rock on a cross or pivot pin 46 mounted in the open end of the support portion 14. One end of the rocker arm 45 bears a fiat surface 48 for engaging a cam 50 integral with and driven by a cam shaft 52. The latter two elements are shown in dot-anddash lines in Fig. l. A spring 49 is conventionally employed between the portion 14 and the rocker arm to urge the surface 48 against the cam.

The other end of the rocker arm 45 bears a slot 54 through which extends an over-center pin, pivot or rod 56 of a toggle mechanism generally indicated at 60.

The toggle mechanism 68 not only includes the overcenter pin 56 but also three links or arms 62, 64 and 66 as well as a slotted cross bar 68 and two springs 70 and 72. An end of each of the arms 62, 64 and 66 is journaled on the pin 56. The other ends of these arms are similarly journaled on either of two pins 74 or 76 arranged parallel with the pin 56 and the diaphragm 32. The pin 74 passes through a slot 80 formed in one end of the arched cross bar 68 and the pin 76 passes through a slot 82 formed in the other end of the cross bar. The rods 74 and 76 are urged toward each other by means of the springs 70 and 72 connecting them.

The arched portion of the cross bar 68 is integrally joined as by welding to a vertical stem or diaphragm actuating means 84 which stem in turn is rigidly fixed to the diaphragm 30 by means of a shoulder portion 86, washers 88 and 90 as well as by dished and opposed diaphragm plates 92 and 94.

In operation of the pump, the spring 49 and the cam 50 will cause oscillation of the rocker arm 45 about the pivot pin 46 and, as a result, the pin 56 is caused to move up and down intermittently with periods of dwell due to the slot 54. The springs 70 and 72 constantly restrain the action of the toggle mechanism 60 in planes parallel with the diaphragm 32. The arms 62, 64 and 66 intermittently spread the rods 74 and 76 apart against the tension of the springs. When the rod 56 is moved beyond the plane in which rods 74 and 76 lie, a snap action occurs making either the quick up or quick down stroke of the diaphragm 32. The slots 80 and 82 in the cross bar 68 permit the buildup of potential energy in the springs 70 and 72 for each pump stroke. As a result, the fluctuating pressure in the pump chamber 30, when plotted against time, presents a wave which is more in the nature of a square wave than a sine wave and this explains the increased capacity of the pump.

It will be noted that horizontal as well as vertical motion of the elements constituting the toggle mechanism 60 is constrained by the diaphragm 32 and that, therefore, no added guides or supports are necessary although they could be used in other designs incorporating the same inventive concept. The cross bar 68 is arched to permit the requisite length of travel for pin 56 as the latter snaps upwardly under the force of the springs 70 and 72.

I claim:

1. A liquid pump including a pump housing comprising a support portion and a pump portion, a diaphragm interposed between said portions and cooperating with said pump portion in defining a pumping chamber, pressure actuated intake and discharge valves associated with said pumping chamber, a rocker arm pivoted with respect to said support portion and having one end extending into the latter, an over-center pin lying in a plae parallel with the plane of said diaphragm, a toggle mechanism including spring means and connecting said pIn to a central portion of said diaphragm, two pins linked to said over-center pin and urged toward each other by said spring means as parts of said toggle mechanism and movable in planes parallel with said diaphragm, and said one end of said rocker arm having a slot through which said over-center pin extends.

2. A liquid pump including a pumping diaphragm interposed between a support portion and a pump housing portion, pressure operated valves controlling flow through a pumping chamber defined by said diaphragm and pump housing portion, oscillating means in said support portion adapted to be power operated, a cross-bar extending parallel to and fixed to said diaphragm, two parallel pins slidably connected to said cross-bar, arms connected to said pins, an over-center pivot linked to said parallel pins by said arms and movable between the parallel pins in a direction toward and away from said diaphragm,

spring means urging said two pins toward each other, and a lost motion connection between said oscillating means and said over-center pivot.

3. A liquid pump including a pump housing, a pumping diaphragm cooperating with said housing in defining a pumping chamber on one side of said diaphragm, pressure actuated valves in said housing controlling fiow through said pumping chamber, a rocker arm arranged at the other side of said diaphragm and adapted to he power actuated, a toggle mechanism connecting said arm to said diaphragm for actuating the latter, said mechanism having a cross arm fixed to said diaphragm and two parallel pins slidably connected to said cross-bar, spring means urging said pins toward each other, an overcenter pin loosely connected to said rocker arm, and links connecting said over-center pin to said parallel pins whereby said over-center pin may move between said parallel pins toward and away from said diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS 1,891,902 Babltch Dec. 27, 1932 1,899,295 Schulze Feb. 28, 1933 "min 

